| 摘要 |
PURPOSE: A digital relay and instrumentation apparatus is provided to improve precision of the apparatus by converting three-phase AC signal and input analog signal to digital signal and outputting control signal. CONSTITUTION: The step down device(10) step downs the three-phase AC signal below predetermined level. The square wave generator(20) transform the step downed three-phase AC signal into the square wave to output it. The waveform detector(30) compares the square wave with reference clock pulse and detects raising timings of the each phase. The analog/digital converter(50) converts the step downed three-phase AC signal and analog signal from a plurality of current transformers into digital signals to output them. The controller(61) is supplied with the raising timings of the each phase and the digital signals, detects phase difference/voltage of the three-phase AC signal and current quantity for the current transformers and compare the current quantity with reference value repetitively to output control signal. The operation panel(70) displays the current quantity, the phase difference/voltage and error message. |
